Rhodophyta-1    

Diversity   Genera -800     Species - 5200

Color  Red -> Black

Varies with Depth

High Intertidal Zone -> Green -> Black

Lower Intertidal Zone -> Brown - Purple

Greater Depths -> Rosy Red

Color depends on Pigment Types & Concentrations

Photosynthetic Pigments

Chlorophyll a, d

Phycobillins - Phycoerythrin & Phycocyanin

Carotenoids -a & b Carotene

Xanthophylls - Leutin & Zeaxanthan

Occurrence

Most species are Marine (96%).

They have a Diverse Distribution & range from Tropical to Cold Waters.

They can be found at depths up to 120 m.

A few Red Algae can be found in cold fast-running Freshwater Streams.

A few species are Terrestrial.

Consequently, they have the Greatest Range for Macroalgae.

Cell Wall

Inner Cellulose Wall

Random Cellulose Fibrils

Granular Matrix

Outer Sheath = Colloidal Substances

Agar (Commercially Important)

Carrageenan (Commercially Important)

Others

These mucilages make up up to 70% of dry weight of the cell wall.

They may protect from desiccation that could occur at low tides.

Geniculate Coralline Rhodophyta

These substances may help otherwise flaccid organisms to become erect.This can have profound ecological significance as erect organisms can gain better access to PAR than prostrate species.

Geniculate Coralline Alga

Coralline Algae

These precipitate Calcium Carbonate in their Outer Wall Layers. This forms a rigid extracellular matrix that contributes to the formation of Coral Reefs.

There are two general types based on their
morphology. These are called Geniculate
and Non-Geniculate.

Geniculate -> branched & flexible due to the presence of Genicula between rigid Intergeniculate segments. This reminds one of Node-Internode.

Non-Geniculate -> These are encrusting
and are generally prostrate.

However some produce small foliose branches,
while others are nodular.